<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <style>
    .demo{
      border: 20px solid;
      border-radius: 50%;
      width: 300px;
      height: 300px;
      border-bottom: transparent;
    }
  </style>
</head>
<body>
  <div class="demo">
    
  </div>
</body>
</html>